1. Field of the Invention
The present general inventive concept relates to an injection molding machine, and more particularly, to an injection molding machine to support a molded piece when molds are disassembled from each other, in order to prevent separation of the molded piece from the mold.
2. Description of the Related Art
An injection molding machine is a machine that produces a molded product by injecting molten resin into a cavity defined by molds and solidifying the resin. There are two types of injection molding machines, one type of which is to produce a molded product through a single molding process using a single material, and the other type of which is to produce a molded product through two or more successive molding processes using two or more materials.
Specifically, a machine to produce a molded product through two successive molding processes is referred to as a double injection molding machine. A double injection molding machine includes a first cavity to form a first molded piece, and a second cavity to receive the first molded piece therein and to secondarily carry out a molding process for the first molded piece. In such a double injection molding machine, the first molded piece formed in the first cavity is moved to the second cavity while being positioned in the molds. Another material is injected into the second cavity containing the first molded piece, to thereby form a double molded piece.
Because the first molded piece formed in the first cavity should be accurately moved to the second cavity, the first molded piece should not be separated from the mold when the molds are disassembled from each other after the first molding process. Also, in a case of a common injection molding machine (not a double injection molding machine), if post processes (e.g., coating, coloring and trimming processes) for the molded piece should be carried out while the molded piece is kept in the molds, preventing separation of the molded piece from the mold is necessary.
An example of a double injection molding machine to prevent separation of a molded piece from a mold when molds are disassembled from each other is disclosed in Korean Utility Model Publication No. 20-188896 (published on Jul. 15, 2000). The disclosed double injection molding machine includes a first cavity formed with recesses, so that protrusions are formed at a first molded piece. Therefore, when molds are disassembled from each other, the protrusions of the first molded piece are kept in a state of being caught by the recesses, and thus the first molded piece is prevented from being separated from the mold. However, because a final molded product produced by the above conventional injection molding machine has unnecessary protrusions, there are problems such that an additional process of eliminating the protrusions from the molded product should be carried out and product quality is deteriorated due to marks of the protrusions.